Animal models have played, and will continue to play, an important role in determining function of individual genes in the pathogenesis of diabetes mellitus. Yet, with the impending availability of the genome sequences for both humans and mice we lack tools and strategies for efficiently assessing the functional importance of various genes of pancreas function and development. During recent years, the Cre/loxP recombinase system has been developed and adapted to the study of genes that play a role in glucose homeostasis. In this project we will further enhance this technology by perfecting the use of a 'dual recombinase' gene targeting strategy that avoid problems associated with the more commonly used 'triple loxP strategy'. In addition, we will strive to utilize the full power of site-specific recombinases as a tool for genetic manipulation in the mouse by developing a system for the rapid insertion of exogenous DNA sequences in the mouse insulin I gene locus. Lastly, we will make use of a novel cell lines that appears to be derived from an islet neogenic precursor cell to try to discover other genes that may be important in pancreas function and/or development. Aim 1 is to determine the functional consequences of the lack of sulfonylurea receptor, type 1 (SUR1) on both beta cell function and islet morphology, and generate mice with a conditional sur1 allele so the acute effects of the absence of SUR1 can be determined. Aim 2 is to develop a method for the rapid insertion of exogenous genes and DNA sequences into the mouse insulin 1 gene locus using the reverse reaction of Cre recombinase. We will use this method to generate mice that express a ligand-inducible Cre-progesterone receptor (CrePR) fusion protein in beta cells. Aim 3 is characterize differences in the gene expression profiles of a newly developed pancreatic islet cell neogenic precursor cell line, with that of pancreatic beta cells and delta cells, using both suppression subtractive hybridization and DNA microarray technologies. We will then determine the consequences of the lack of one or more of these genes in mice using a Cre/loxP gene targeting strategy.